1. Field of the Invention
The present invention relates to ultrasound diagnostic equipment, more particularly, to ultrasound diagnostic equipment for diagnosing a region of interest of an organ by using a scattering coefficient and an attenuation slope of the region of interest.
2. Description of the Related Art
Recently, in accordance with progress in diagnostic techniques using an ultrasound wave, it has become necessary that diagnostic accuracy be improved by using diagnosis of acoustic characteristics of tissues, instead of a conventional diagnostic method for diagnosing from the shapes of internal organs or tumors. Now, acoustic characteristics of tissues, especially an attenuation coefficient (an attenuation slope) and a scattering coefficient (a differential scattering crosssection per unit volume), are used to indicate the characteristics of tissues. These coefficients are useful for detecting a diffuse disease and a cancer in a liver. The scattering coefficient is particularly useful for detecting a myocardial infarction. However, it is difficult to measure the above coefficients with high accuracy and to use these coefficients for practical diagnosis. Namely, when detecting an attenuation slope of the region of interest, a scattering coefficient thereof should be supposed to a specific fixed value, and conversely, when detecting a scattering coefficient of the region of interest, an attenuation slope thereof should be supposed to a specific fixed value.
Therefore, an accuracy of measurements of acoustic characteristics by radiating an ultrasound wave to an organ, receiving a scattered wave and calculating from the scattered wave, is not sufficient. Namely, it is difficult to determine the attenuation slope and the scattering coefficient exactly.
In a manner of speaking, the tissue of an organ is like gelatin including a plurality of particulates floating therein. Thus a power spectrum, a center frequency and an amplitude calculated by using a fast Fourier analysis of ultrasound scattered signals of one scanning line, have large stochastic variance. Therefore, acoustic characteristics calculated by using the power spectrum, the center frequency and the amplitude cannot have sufficient accuracy.